[time-nuts] Phase microstepper designs?

Richard (Rick) Karlquist richard at karlquist.com
Wed Dec 9 11:05:58 EST 2015

On 12/9/2015 2:26 AM, Attila Kinali wrote:
> Moin,
> I just tried to figure out how phase microsteppers are usually build,
> but, beside the time-nuts discussion from 10 years ago and US patents
> US4358741 and US4417352 my search turned out empty. I am pretty sure
> that I used the wrong search terms and there should be lots of documentation
> out there. Can someone give me a hint what to look for?
> 			Attila Kinali

My extensive experience with digging up old articles (before the 
internet, the library was like my second office) is that when
the trail goes cold on some topic for no apparent
reason, it turns out that there is a (non-apparent) good reason
why no one is writing about the topic any more.  I usually
got to the bottom of this by asking experts in the industry.

My general impression about phase microsteppers based on when I
was involved in the time industry is that they didn't have a
very good reputation and were an inferior solution that was
used as an expediency because it it could be "bolted on"
to an existing system that wasn't originally designed to be
tuned.  I think the concensus was that direct digital synthesis
is the better way to go, assuming you can design it into the
architecture in the first place.  DDS is a pretty well developed
technology at this time that is supported by good OTS chips,
so it is not clear what the value proposition would be for
phase microsteppers.

When we were designing the 5071A 25 years ago, it was clear
that the method of tuning by varying the C field was not
acceptable for a state of the art standard.  There are
multiple reasons for this decision.   At the time,
there were a few DDS chips, but we had to roll our own DDS
due to the stringent and specialized requirements.  It took
a whole PC board for this circuit at the time.  The possibility
of using a phase microstepper was never even considered AFAIK.

Are you aware of some redeeming value that phase microsteppers
have that would make us want to investigate them?   Am I
being too harsh on them?  Maybe you can champion them and they
will make a come back :-)

Rick Karlquist N6RK

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